Metallic Sandwich Diaphragm Pump Mechanism

ABSTRACT

A diaphragm pump including a pump head having at least one body plate with a pumped fluid face and at least one body plate with a drive fluid face, a diaphragm assembly positioned between the pumped fluid face and the drive fluid face, and the pumped fluid face having a positive profile biasing the diaphragm assembly in a direction toward the drive fluid face.

I. FIELD AND BACKGROUND OF INVENTION

The present invention relates to pumps, and in particular to diaphragm type pumps. Diaphragm pumps are known in the art, for example U.S. Pat. Nos. 5,279,504 and 6,327,960 illustrate prior art diaphragm pumps. However, there is nevertheless a need for diaphragm pumps which are more economical to construct and offer improved performance characteristics.

II. SUMMARY OF SELECTED EMBODIMENTS OF INVENTION

One embodiment of the invention is a diaphragm pump including at least three body plates and at least two diaphragm assemblies positioned between the at least three body plates. A series of drive fluid passages communicate with a drive side of the two diaphragm assemblies and a series of pumped fluid passages communicate with a pump side of the two diaphragm assemblies. There is an inlet check valve communicating with said series of pumped fluid passages and an outlet check valve communicating with said series of pumped fluid passages. In one alternative embodiment, at least one of the body plates is a doubled faced plate having either drive fluid passages on both faces or pumped fluid passages on both faces.

Another embodiment of the invention is a diaphragm pump which comprises a pump head including at least one body plate with a pumped fluid face and at least one body plate with a drive fluid face. A diaphragm assembly positioned between the pumped fluid face and the drive fluid face, and biasing mechanism biases the diaphragm assembly toward the drive fluid face. In one example, the biasing mechanism is a positive profile on the pumped fluid face which biases the diaphragm assembly in the direction toward the drive fluid face.

III. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of one embodiment of the diaphragm pump, including a reservoir and a driver.

FIG. 2 is an exploded view of one embodiment of the diaphragm pump.

FIG. 3A is an exploded view showing a drive fluid face of a body plate.

FIG. 3B is a perspective view of an alternate strainer plate.

FIG. 4 is an exploded view showing a chemical fluid face of a body plate.

FIG. 5 is an enlarged view of one embodiment of the diaphragm assembly.

FIG. 6 is a cross-section showing one example of a leak detection path.

FIG. 7 is a first cross-section of the FIG. 1 diaphragm pump illustrating the drive fluid passages.

FIG. 8 is a second cross-section of the FIG. 1 diaphragm pump illustrating the pumped fluid (or chemical) passages.

FIGS. 9A to 9C illustrate one embodiment of a pressure gauge assembly.

FIG. 10 is a cross-section of an alternative embodiment of the diaphragm pump.

FIG. 11 A is an end view of one embodiment of a three part “sandwich” diaphragm pump mechanism and one type of driver for the same.

FIG. 11B is side view of the sandwich diaphragm pump of FIG. 11A.

FIG. 12 is a cross-sectional view of the sandwich diaphragm pump of FIG. 11B.

FIG. 13A is a cross-sectional view of one embodiment of a bushing and plunger assembly.

FIG. 13B is a cross-sectional view of another embodiment of a bushing and plunger assembly.

FIG. 13C is a perspective view of the plunger/collar assembly of FIG. 13B.

FIG. 13D is a cross-sectional view of the plunger/collar assembly of FIG. 13B.

FIG. 13E is an end view of the plunger/collar assembly of FIG. 13B.

FIG. 14 is a cross-sectional view of one embodiment of a “burp valve.”

FIG. 15A is a cross-sectional view of one embodiment of a biased sandwich diaphragm assembly.

FIG. 15B is a enlarged view of a portion of the sandwich diaphragm of FIG. 15A.

FIG. 16A is a cross-section view showing the location of one embodiment of an internal relief valve combined with a fluid leak indicator.

FIG. 16B is an enlarged cross-sectional view of the internal relief valve combined with a fluid leak indicator seen in FIG. 16A.

FIG. 17 is a schematic cross-section of an alternate method of securing a diaphragm assembly between body plates within a pump head.

FIGS. 18A is a schematic cross-section of a further alternate method of securing a diaphragm assembly between body plates within a pump head.

FIG. 18B is planar view of a ring of wedge members utilized to tension the diaphragm assembly.

FIG. 19 is schematic diagram of a sensor monitoring circuit utilized in one embodiment of the invention.

IV. DETAILED DESCRIPTION OF SELECTED EMBODIEMTNS

FIG. 1 illustrates one embodiment of the present invention, the diaphragm pump 1. In FIG. 1, the diaphragm pump is illustrated being used in combination with fluid reservoir 80 and driver or motor 100, but neither the motor, nor the reservoir need form part of the present invention. The motor 100 seen in FIG. 1 is a pneumatic, pilot valve controlled motor such as disclosed in U.S. Pat. No. 6,736,046, Pilot Control Valve Utilizing Multiple Offset Slide Valves, which is incorporated by reference herein in its entirety. Motor 100 includes the pilot valve 101 which controls pressurized air driving piston 102 in a reciprocating manner. Piston stem 103 transmits the reciprocating force to the equipment being driven by motor 100. The u-cup seal 104 prevents the loss of air pressure from around piston stem 103 to the exterior of motor 100. While the illustrated motor is a pilot controlled pneumatic motor, virtually any motor providing reciprocating motion, whether pneumatic, hydraulic, electric, or otherwise, could be employed.

The illustrated embodiment of fluid reservoir 80 is formed of a reservoir body 83 which includes a fluid space 88, a drive side 82 which makes a sealed connection with motor 100, and a pump side 81 which makes a sealed connection with diaphragm pump 1. This embodiment of reservoir body 83 further includes the vent plug 86 and drain plug 87. Vent plug 86 allows the fluid in the fluid space 88 to remain at the exterior ambient pressure (e.g., atmospheric). Extending through reservoir body 83 is plunger 90. On one end, plunger 90 is connected in a conventional manner (e.g., mating threads) to the piston stem 103 of motor 100. The quad-ring seal 93 acts to prevent movement of fluid from reservoir space 88 into motor 100's interior. The end of plunger 90 opposite piston stem 103 engages and is sized to move within the drive fluid passage 85 formed in reservoir body 81 This end of piston stem 103 includes the center passage 92 which is open to the end of plunger 90 and extends into plunger 90 at least as far as the series of radial passages 91 which extend transversely through the diameter of plunger 90. Thus, it will be understood that when radial passages 91 are outside of drive fluid passage 85 (as suggested in FIG. 1), there is a fluid path from reservoir space 88, through radial passages 91, center passage 92, and into drive fluid passage 85. In preferred embodiments, the drive fluid is an oil such as a conventional hydraulic fluid or a mineral oil.

The embodiment of diaphragm pump 1 seen in FIG. 1 generally comprises a series of body plates 5 with diaphragm assemblies 50 positioned between the body plates. FIGS. 2 and 7 better illustrate how this embodiment includes four body plates 5A to 5D. As best seen in FIG. 2, a series of bolts 38 pass through apertures 39 in body plate 5A to 5C, engage threaded apertures in body plate 5D, and secure the body plates together. The body plates 5 may be constructed of any material suitable to the pressure and corrosive conditions of anticipated use. In one non-limiting embodiment, certain body plates exposed to corrosive fluids are constructed of a corrosion resistant material (e.g., 316 stainless steel) while other body plates exposed only to drive fluid may be constructed of a stronger and/or less expensive material (e.g., 4140 steel). The body plates 5 will typically have a series of internal passages (described in detail below) allowing fluid to move between the perimeter area 6 of the body plate to at least one face 7 of the body plate. As is common with most diaphragm pumps, a first fluid or a “drive” fluid will act on one side of the diaphragm(s) to cause displacement of the diaphragm. In FIG. 1, the drive fluid originates in reservoir 80 and is placed under pressure by plunger 90. A second fluid or a “pumped” fluid is moved through the pump by displacement of the diaphragm. The pumped fluid is the fluid being employed in the chemical, industrial, or other process utilizing the pump. When referring to a side of a diaphragm or a face of a body plate exposed to drive fluid, this may be described as the “drive fluid side” of the diaphragm or body plate. Likewise, the side of a diaphragm or a face of a body plate exposed to pumped fluid, may be sometimes described as the “pumped fluid side” of the diaphragm or body plate. As the pumped fluid is typically a chemical composition, the pumped fluid side is more often simply referred to as the “chemical side” of the diaphragm or body plate face.

FIG. 10 illustrates a slight modification to the embodiment seen in FIG. 1. In FIG. 10, the plunger 90 is solid, i.e., does not have the center passage 92 or the radial passages 91 formed in the plunger. Rather, the radial passage 91 in FIG. 10 is placed through the section of the reservoir wall forming drive fluid passage 85. Additionally, the FIG. 10 embodiment illustrates the addition of a replaceable bushing 105 between plunger 90 and the interior wall of drive fluid passage 85. In one example, replaceable bushing 105 is formed of a material such as steel or a ceramic.

FIG. 7 is a cross-section illustrating a series of internal passages in the body plates 5 on the drive fluid side 9 of the body plates. Depending on their position, different body plates may have different sets of passages. For example, body plate 5B is seen having co-planar passages 12 (i.e., passages generally in the plane of the plate) on each face and traverse passages 13 passing though the plate generally perpendicular to the co-planar passages. On the other hand, body plate 5D has the main drive fluid inlet 34 (which joins with the drive fluid passage 85 of reservoir 80 as seen in FIG. 1), a short transverse passage 13, and a co-planar passage 12 for further distributing drive fluid to other body plates. The embodiment of FIG. 7 further illustrates how the tubular connector bushing 22 forms part of a transverse passage 13 traversing body plate 5C. Connector bushing 22 includes o-rings 23 and backup rings on each end which seal with body plates 5B and 5D. Although connector bushing 22 is one example of an efficient manner to establish a fluid path through body plate 5C, there are of course other conventional techniques for creating such a sealed fluid path.

The path of drive fluid into diaphragm pump 1 is apparent in FIG. 7. Fluid enters inlet 34 of body plate 5D where it is directed to diaphragm assembly 50 via the short transverse passage 13. Drive fluid is also directed via co-planar passage 12 in body plate 5D, through hydraulic bushing 22, into co-planar passage 12 and transverse passages 13 in body plate 5B, where the fluid ultimately acts against the two diaphragm assemblies 50 facing body plate 5B. It can be seen in FIG. 7 and FIG. 2 how a series co-planar passages 12 are formed on the faces of body plate 5B adjacent to diaphragm assemblies 50 in order to distribute drive fluid against the drive side of the diaphragm assemblies 50. It will be understood that these are the terminal end of the drive fluid passage and sometimes are themselves referred to as drive fluid passages. Likewise, the entire path from inlet 34 to passages 12 on the face of the body plates may be considered the drive fluid passage. It can be seen how in the illustrated embodiment, co-planar passages 12 (including passages on the faces of the body plates) and transverse passages 13 form a means for distributing drive fluid against the diaphragm assemblies. As suggested above and illustrated in the FIG. 7 embodiment, body plate 5B has both faces configured to distribute drive fluid against the diaphragm assemblies, whereas body plate 5D (the body plate closest to plunger 90) only has one face configured to distribute drive fluid against the diaphragm assemblies. Nevertheless, the figures illustrate merely one preferred embodiment and not all embodiments need have double faced body plates, single faced body plates, or a combination of the two.

The embodiment of diaphragm assemblies 50 seen in the figures is perhaps best understood with references to FIGS. 4 and 5. In this embodiment, the diaphragm assembly includes three separate diaphragm “layers” (i.e., separate individual diaphragms), chemical side diaphragm layer 51, center diaphragm layer 52, and drive side diaphragm layer 53. Additionally, the strainer plate 54 is positioned against the drive side diaphragm layer 53. The strainer plate serves at least two primary functions. First, it tends to more evenly distribute the pumped fluid. Second, it provides a more robust surface for sealing against the o-ring 57 (see FIG. 7) on the pumped fluid face 8 of the body plates. In one preferred embodiment, strainer plate 54 has a flat side abutting against the body plate and a slight concave curvature abutting the diaphragm layers. FIG. 4 suggests how strainer plate 54 includes a series of apertures 55. FIG. 3A shows the opposite face of strainer plate 54 seen in FIG. 4. FIG. 3A illustrates a web of grooves 56 which communicate with apertures 55 and act to distribute drive fluid across the face of strainer plate 54 which rests against diaphragm layer 53. FIG. 3A also illustrates a series of annular sealing grooves 58 formed near the perimeter of strainer plate 54. These sealing grooves 58 are best seen in the detail of FIG. 6. This detail shows sealing grooves 58 on strainer plate 54 engaging diaphragm layer 53 and similar sealing grooves 58 on the face of body plate 5C engaging diaphragm layer 51. It can be understood how these grooves 58 form a seal with the diaphragm layers when opposing body plates are compressed together by bolts 38 (FIG. 2).

FIG. 3B illustrates an alternative strainer plate 154 and in particular, the side of of strainer plate 154 facing the diaphragm assembly. This side of strainer plate 154 includes the raised center portion 158 which may in certain instances tend to eliminate dead space between the strainer plate and the diaphragm assembly. This embodiment of the strainer plate includes a circumferentially oriented channel 156 which, at least partially, extends around raised center portion 158. A series of radially oriented channels 157 extend from raised center portion 158 toward circumferentially oriented channel 156, although FIG. 3B also shows one radially oriented channel 157 which does not intersect channel 156. FIG. 3B also illustrates several through-apertures 155 intersecting circumferentially oriented channel 156. In the FIG. 3B embodiment, circumferentially oriented channel 156 is positioned on the “upper” half of strainer plate 154, i.e., “upper” meaning higher relative to the direction of gravitational force.

In one preferred embodiment, each diaphragm layer is an approximately 10 mil thick sheet of 316 stainless steel. However, the diaphragms could be made of any number of suitable materials, including as nonlimiting examples, steel or an elastomer material. Diaphragm assembly 50 could alternatively be formed of one, two, or more than three diaphragm layers. One example of strainer plate 54 is a 125 mil sheet of stainless steel with the above described apertures and grooves formed therein.

FIG. 7 also illustrates, a series of bleed passages 19 which have both a co-planar component and a transverse component within the body plates 5. One end of the bleed passages are in fluid communication with either the drive fluid side of the diaphragm assembly or the chemical side of the diaphragm assembly, while the other end of the bleed passages terminate with bleed screws 75. The bleed passages provide paths for air to be forced out of the pump when priming the pump (i.e., filling it with fluid) prior to commencing operation. One preferred embodiment of bleed screws 75 include the bleed poppet 76 and biasing spring 77. The bleed poppet 76 and spring 77 function to provide slight resistance when air is being removed. When a bleed screw 75 is loosened, poppet 76 may move against spring 77 to open the bleed passage. When the bleed screw 75 is tightened, poppet 76 is held in the closed position. As suggested above, the bleed passages are in communication with both the drive fluid side of the diaphragm assemblies 50 and the chemical side of the diaphragm assemblies 50 in order to allow air removal on both sides of the diaphragm assemblies.

FIG. 8 is another cross-section of diaphragm pump 1 which illustrates the internal passages associated with the chemical side of the diaphragm assemblies 50. The chemical or pumped fluid enters the diaphragm pump 1 via a one-way valve which is in this embodiment, check valve 41. Check valve 41 is an “intake” or “inlet” valve in the sense that fluid can flow into pump 1 through this valve, but is blocked from flowing out of pump 1 through this valve. As suggested in the detail of FIG. 8, this embodiment of check valve 41 is a poppet type check valve generally including the poppet and spring configuration of FIG. 9C. Of course, many other conventional or future developed one-way valves could be employed in the alternative. Fluid entering check valve 41 will be directed through the chemical co-planar passages 16 (via connector bushing 22 in the case of the co-planar passage in body plate 5C). The body plates 5A and 5C further have a series of distribution passages 18 communicating between the co-planar passages 16 and the chemical faces 30 of the body plates. As is visible on close inspection of FIG. 8, chemical faces 30 have a slight concave or inward (toward distribution passages 18) curvature. For example, in the embodiment of diaphragm pump 1 where the diaphragm assemblies 50 have a diameter of approximately four inches, the radius of curvature of the chemical face may be about 32 inches (i.e., a 32 inch radius of curvature). Obviously, this is merely one example radius of curvature and this may vary greatly based on different facts, including the diameter of the diaphragm assembly 50 (e.g., larger diaphragm assembly diameters will generally correspond with a greater radius of curvature). It can also be seen in FIG. 8 that the co-planar passages 16 communicate with a discharge one-way valve, again the check valve 40 in this embodiment. As with the drive fluid passages, connector bushings 22 form a chemical fluid passage through body plate 5B. Thus, the chemical fluid passage traverses through body plate 5B which has drive fluid faces. Check valve 40 is similar in construction to the poppet type check valve 41 described above and is a “discharge” valve in that it allows flow only in a direction out of pump 1. The check valves form a means for allowing one-way fluid communication. In the illustrated embodiment, the diaphragm pump has a single inlet check valve 41 in body plate 5A and a single outlet check valve 40 in a different body plate 5C. However, other embodiments could have multiple inlet/outlet check valves in the same or different body plates. The path from the inlet check valve, to the chemical side of the diaphragm assemblies, and to the outlet check valve, may be considered as the pumped fluid (or chemical fluid) passage.

Another aspect of the illustrated embodiment is a diaphragm leak detection technique best understood viewing FIGS. 4 and 6. FIG. 4 suggests how diaphragm layers 52 and 51 have a leak detection aperture 62 as does body plate 5C. Thus, if diaphragm 51 ruptured or otherwise leaked fluid, a fluid path exists between diaphragm layer 51 and 52, through their apertures 62, and ultimately to the leak aperture 62 in body plate 5C. This leak detection path is better seen in the cross-section of FIG. 6. The detail insert illustrates how fluid may travel between diaphragm layers 51 and 52 and ultimately into leak detection passage 67 in body plate 5C. As the leaked fluid fills passage 67, the increasing pressure will be registered by pressure gauge 65, thus notifying operators of a leak issue. Additionally, FIG. 4 shows the alignment pin 64 engaging the diaphragm assemblies 50 and body plates 5 through the alignment apertures 63. The alignment pins 64 ensure that the leak detection apertures through the diaphragm layers and into the leak detection passages of the body plates are all properly aligned.

One embodiment of pressure gauge 65 is seen in more detail in FIGS. 9A to 9C. This pressure gauge 65 will include gauge stem 69 which houses poppet 70 biased in the closed position by spring 77. When pressure on poppet 70 is sufficient to overcome the force of spring 77, poppet 70 will be lifted and o-ring 72 moved out of the sealing position. Fluid may flow through poppet apertures 71 and the gauge stem 69 to act on the pressure sensing elements of the gauge. A bleed screw 75 and ball 78 also engage valve stem 69. It can be seen how tightening of bleed screw 75 causes ball 78 to block the passage through bleed screw 75 and how loosening of bleed screw 75 would allow space for fluid to flow around ball 78 and out of the bleed screw.

The operation of the pump will be described by starting with FIG. 1. As suggested above, driver 100 will move plunger 90 in a reciprocating path within drive fluid passage 85. On the suction stroke, plunger 90 will be withdrawn from fluid passage 85 to the extent needed to expose radial passages 91 to reservoir space 88. This action simultaneously produces a slight vacuum in fluid passage 85 such that fluid in reservoir space 88 is drawn into radial passages 91, through center passage 92, and into drive fluid passage 85. On the power stroke, plunger 90 moves toward diaphragm pump 1 and the radial passages 91 enter the confines of fluid passage 85. Because of the close tolerance between the outer diameter of plunger 90 and the inner diameter of fluid passage 85, the drive fluid in passage 85 is pressurized as plunger 90 moves toward pump 1. The magnitude of the pressure imparted to the diaphragm assemblies is regulated by controlling the distance plunger 90 extends into fluid passage 85. For example, in the embodiment of FIG. 1, the end of plunger 90 threading into piston stem 103 allows rotation of plunger 90 to shorten or lengthen plunger 90 relative to piston stem 103, and thus plunger 90's travel into fluid passage 85.

Viewing FIG. 7, the pressurized drive fluid is transmitted through co-planar passages 12 and transverse passages 13 to ultimately impart force against the drive fluid side of diaphragm assemblies 50. Viewing FIG. 8, the diaphragms 51 to 53 will flex toward the curvature 30 in the chemical face of the body plates. This pressurizes the fluid on the chemical side of pump 1 and will cause the discharge of a given volume of fluid from discharge check valve 40. On the suction stroke of plunger 90 (FIG. 1), a lower pressure condition tends to be formed on the drive fluid side of pump 1 and the diaphragms 50 are pulled away from the chemical face of the body plates. This action lowers the pressure on the chemical side of pump 1 and will draw in a given volume of fluid through intake check valve 41. The pump phase will then be repeated as plunger 90 transitions back to a power stroke.

In the illustrated embodiments, the diameter of all the body plates is equal or approximately equal, as is the diameter of all the diaphragm assemblies. However, this feature is not required for all embodiments. The diameters of the body plates or diaphragm assemblies are considered approximately equal if they are within, alternatively 5%, 10%, or 20% of one another. PCT Serial No. PCT/US14/60077, filed Oct. 10, 2014 and entitled, “Scalable Pumping Mechanism Utilizing Anti-Synchronized Poly-Diaphragm Stack,” is incorporated by reference herein in its entirety.

FIGS. 11A and 11B are end and side views respectively of one embodiment of the “sandwich diaphragm” pump mechanism of the present invention. These figures generally show the pump head 201 and driver 300 positioned on support base 310. There is a “burp well” 295 (explained in more detail below) and a pressure gauge 265 which indicates pressure of any fluid reaching the leak detection diaphragm/circuit.

FIG. 12 is a cross-sectional view of the pump orientation seen in FIG. 11B. The pump head 201 generally includes the single faced pumped fluid body plate 205A and the single faced drive fluid body plate 205D. In this embodiment, the reservoir body 283 is integrally formed with body plate 205D and the support base 310 is affixed to body plate 205D. Body plate 205A includes the discharge check valve 240 and the intake check valve 241 as in previous embodiments. Differing somewhat from earlier embodiments, body plate 205D includes the burp well 295 within which is positioned burp valve assembly 315 (explained in more detail below) and the bushing 284.

The driver 300 is formed of the driver housing 301 within which cam shaft 302 converts rotational motion (e.g., from an electric motor) to linear reciprocating motion through connecting rod 303 and slider piston 304. This in turn is connected to plunger 290 via piston extension arm 308 and collar 307. Alternate embodiments could provide linear reciprocating motion through other means, such as a pneumatically powered reciprocating driver, an electrically-actuated solenoid-type assembly, or any other drive mechanism that produces reciprocating motion.

FIG. 13A is an enlarged sectional view illustrating bushing 284. It may be seen that bushing 284 is fixed within body plate 205D by retainer ring 289 along with seals 288. A central or main plunger passage 291 extends through bushing 284 and is engaged by plunger 290. A series of cross passages 285 are formed through bushing 284 and these cross passages 285 communicate between main passage 291 and annular space 286. As best seen in FIG. 12, the annular space 286 ultimately communicates with reservoir 280 via reservoir conduits 287.

In one embodiment, bushing 284 and plunger 290 are formed of a ceramic material, and more preferably a Zirconia Y_TZP ceramic. However, other ceramic material my be acceptable, as are a variety of metallic materials, provided they have sufficient strength, hardness, and dimensional stability such that they can be machined within highly precise tolerances. In one embodiment, main plunger passage 291 has a tolerance of less than 0.5/1000 of an inch (0.0005 in.), diametrically, with respect to the plunger 290. More preferably, a tolerance of less than about 0.25/1000 of an inch (0.00025 in.) is desirable. In the most preferred embodiments, the bushing and plunger are fitted as a matched pair in order that each bushing/plunger combination will enable essentially identical, extremely small annular areas within the limitations of whatever measuring equipment is being employed. FIG. 13A suggests how a collar 307 may be used to attach the enlarged head of plunger 290 to the extension arm 308 of piston 304. Collar 307 will be sized to create a tolerance or “gap” between the inner diameter of collar 307 and the outer diameter of the head of plunger 290 (see gap suggested by 309 in FIG. 13A). This gap allows plunger 290 to shift slightly in the instance where the center line of the piston extension arm is not precisely aligned with the center line of the main passage 291. In one example, the gap 309 is approximately 0.025 to 0.050 inches.

A somewhat different bushing/plunger arrangement is seen in the alternate embodiment of FIG. 13B. In this embodiment, the bushing is formed of an inner ceramic portion 248B and and outer metal (e.g., stainless steel) portion 248A which has been thermally press fit to the ceramic portion 248B. Bushing 248 is fixed in place between front retaining ring 289 and conical retaining member 311, which is in turn secured by rear retaining ring 313. Conical retaining member 311 includes the equalization passages 312 to avoid any pressure differentials between the two faces of conical retaining member 311. FIG. 13B also illustrates a modified collar/plunger assembly, which is seen more clearly in FIGS. 13C to 13E. FIG. 13C illustrates how plunger head 330 includes a series of retaining lugs 332. Collar 307 includes a corresponding series of front retaining walls 333 and the lug channel 334 behind retaining walls 333. Projecting from a rear inner wall of collar 307 is the spring loaded locking pin 329. It may be envisioned from FIGS. 13C to 13E how plunger head 330 is inserted into collar 307 such that the retaining lugs 332 depress locking pin 329 and rest in lug channel 334 behind retaining walls 333. Rotation of plunger head 330 then locks retaining lugs 332 behind retaining walls 333 as locking pin 329 engages one of the pin grooves 365 on plunger head 330. FIG. 13D illustrates the locked position of locking pin 329 and also illustrates tolerance gap 309 allowing for the above described slight repositioning of plunger 290 relative to passage 291.

FIGS. 15A and 15B show one embodiment including pumped fluid body plate 205A, diaphragm assembly 250, strainer plate 254, and drive fluid body plate 205D. The bolts 238 are also shown engaging drive fluid body plate 205D and ultimately engage a far side of pumped fluid body plate 205A (as seen in FIG. 11B). As in previous embodiments, this “sandwich” diaphragm assembly includes three separate metal diaphragms, with the middle diaphragm acting as a leak detection diaphragm. In the FIG. 15 embodiment, the sandwich diaphragm assembly 250 positioned between the pumped fluid face 208 (of pumped fluid body plate 205A) and the drive fluid face 209 (of drive fluid body plate 205D) will take on a curved shape with the center of the diaphragm assembly being closer to the drive fluid face 209 than the pumped fluid face 208, i.e., the diaphragm assembly takes on a convex shape with respect to the pumped fluid face 208. In this embodiment, the side of strainer plate 254 facing diaphragm assembly 250 will have a convex shape (with respect to the pumped fluid face 208) and the side of strainer plate 254 facing drive fluid face 209 will be flat. As one nonlimiting example, where the strainer plate is approximately 4 inches in diameter, the strainer plate could have a maximum thickness at its edges of 0.160 inches and a minimum thickness at its center of 0.120 inches. In this example, the convex face of the strainer plate could be at least 0.04 inches deep and be formed using multiple radii of curvatures. Naturally, many different depths and curvatures could be used in alternative examples. Because of the curvature of diaphragm assembly 250, FIG. 15A shows the interface (or seam) line 215 between the body plates near the center of the fluid faces, but the interface line 215 is covered by the diaphragm assembly 250 at the outer radial edges of the fluid faces.

Many prior art diaphragm pumps apply high clamping stress to the outer edge of a sandwich diaphragm in order both to secure it in position and to resist the high pressures developed by the liquids on both sides of the sandwich diaphragm. These clamping forces invariably generate stresses that exceed the yield strength of the diaphragm materials, leading to plastic deformation (irreversible strain) during the initial application of clamping at their edges. Some of this deformation is directed inwards, causing the diaphragms invariably to “wrinkle” or “oil can”—leading to inconsistent starting positions which are been impossible to predict and which vary per assembly. The biased diaphragm assembly utilized in certain embodiments described herein solves this problem by ensuring a predictable starting position.

Many different techniques could be employed to obtain this convex shape of diaphragm assembly 250. In the FIG. 15 embodiment, the pumped fluid face 208 will have positive profile 211 biasing the diaphragm assembly in a direction toward the drive fluid face 209. The profile is “positive” in the sense that the profile is formed by a portion of the pumped fluid face 208 which is closer to drive fluid face 209 than other portions of pumped fluid face 208. For example, FIG. 15A shows the positive profile 211 being formed on the outer radial half of the pumped fluid face 208, i.e., the surface of the pumped fluid face one half the radius or further from the center point of the face. In one embodiment, this outer radial positive profile is generally convex with a radius of curvature R₁. As is also seen in FIG. 15A, the inner radial half of pumped fluid face 208 has forms a concave portion of pumped fluid face 208 with a radius of curvature R₂. As one non-limiting example, for a pumped fluid face having a diameter “D” of 4 inches, the outer radial convex portions have a radius of curvature R₁ of approximately 25 inches while the inner radial concave portions have a radius of curvature R₂ of approximately 6 inches. Naturally these radii and daimeters could vary in different embodiments for different pumping volume requirements or to further optimize preferred embodiments over time as field experience might dictate. Different pumping volumes require different pumped fluid face diameters or other means to change the size of the pumping chamber.

In prior art pumping mechanisms, the problem of entrained gas bubbles on the hydraulic (i.e., drive fluid) side of the diaphragm have been dealt with in various ways. Gas bubbles may consist of entrapped atmospheric air from when the pump is initially commissioned, or during subsequent filling after servicing, or when the level of the drive liquid gets too low. Gas bubbles may also form at various times during operation, when the drive liquid itself momentarily reaches a particular temperature and pressure combination such that it vaporizes (reaches its “vapor pressure”). Vapor pressure of the drive liquid is dependent on the exact chemical composition of the liquid and is directly proportional to the temperature of the liquid. Most contemplated drive liquids have negative vapor pressure (vacuum) at atmospheric pressure and normal ambient temperatures. Higher temperatures can cause vapor pressure to rise and even become positive. Large changes in drive liquid velocity causes low pressures, sometimes below its vapor pressure, creating entrained gas bubbles. In essence, it “boils.” In any positive displacement pump, entrained gas immediately degrades the efficiency of the pumping action and should be removed as quickly as possible, hence the need for continuous “burping.”

One embodiment of the present invention is a diaphragm pump which includes a “burp valve” assembly. FIG. 12 generally shows a burp valve assembly 315 positioned within a burp well 295. Typically, burp well 295 will be filled with drive fluid (e.g., a liquid such as hydraulic oil) and is in communication with fluid reservoir 280 via reservoir return line 296. FIG. 12 demonstrates how air bleed line 326 will allow hydraulic fluid and entrained gas bubbles to move from the pumped fluid side of the diaphragm assembly to burp valve assembly 315.

FIG. 14 illustrates burp valve assembly 315 in more detail. Generally, burp valve assembly 315 includes a burp valve housing 316, which encompasses burp valve seat 317 retained in housing 316 by valve cap 318. A ball lower seat 322 is formed in the bottom of valve housing 316 and communicates with air bleed line 326. A ball upper seat 321 is formed in the bottom of valve seat 317. It will be understood that when fluid pressure forces ball 323 against either lower seat 322 or upper seat 321, ball 323 will block flow through that seat. In one preferred embodiment, the distance between the upper and lower seats 321 and 322 is less than twice the diameter of the valve ball 323. The seals 324 prevent fluid flow between valve housing 316 and valve seat 317 in the area adjacent to the ball upper seat 321. However, a fluid path does exist between the interior of valve seat 317 and the exterior of valve housing 316 via the seat apertures 327 and housing apertures 328. A burp valve poppet 320 is positioned in valve seat 317 and has a upper portion which extends through valve cap 318. The spring 319 within valve seat 317 acts to bias valve poppet 320 upward against valve cap 318. Valve poppet has sufficient length such that when its upper portion is pressed downward toward valve cap 318, the lower portion of the valve poppet is able to push ball 323 out of engagement with ball upper seat 321.

It may be envisioned from FIG. 14 how air bubbles in drive fluid will travel up air bleed line 326 and encounter ball 323. Normally any significant fluid pressure (e.g., the positive pressure stroke on the drive fluid side of the diaphragm) will move ball 323 into engagement with upper seat 321 and prevent the movement of fluid through burp valve assembly 315. However, the release of positive fluid pressure (e.g., the negative pressure stroke on the drive fluid side) will allow ball 323 out of engagement with upper seat 321. This up and down movement of ball 323 will effectively function as a shuttle valve and will typically allow bubbles in air bleed line 326 to move between the ball seats and eventually through the burp valve assembly into the burp well. There may be situations, such as initially filling the pump with drive fluid, where hydraulic fluid containing air bubbles will maintain ball 323 against upper seat 321 and prevent the passage of the air bubbles through the burp valve assembly. In such cases, the upper portion of the valve poppet may be manually depressed, forcing ball 323 out of engagement with upper seat 321. Multiple depressions of valve poppet 320 should be sufficient to allow air bubbles to move around ball 323 and into the burp well. Although not explicitly shown in the Figures, it will be understood that drive fluid will typically be found in the burp well and will at least partially cover the burp valve assembly.

Another aspect of the present invention is illustrated in FIGS. 16A and 16B. Shown in these figures is a drive fluid over-pressure relief and indication system. Over-pressure detection is advantageous because over-pressure relief valves are not designed, nor can they be, to actuate repeatedly for an infinite number of cycles. Additionally, over-pressuring of the drive fluid is an abnormal condition which needs to be addressed as soon as possible. For these reasons the present invention seeks not only to relieve the over-pressure condition before pump components are damaged, but also to indicate immediately that the condition exists so it can be dealt with appropriately. The over-pressure relief and indication system generally includes an internal relief valve (or “IRV”) 350 and an indicator assembly 335. Looking first at IRV 350, the IRV includes a valve bore 361 formed into the drive fluid body plate 205D. As seen in FIG. 16B, the rear of valve bore 361 communicates with a fluid passage 362, which in turn communicates with the drive fluid face 209. Valve bore 361 also communicates with a side passage 342 extending between valve bore 361 and the indicator assembly 335. An IRV body (or housing) 351 is positioned within valve bore 361 and includes a central passage terminating with the IRV ball seat 359 and inlet channel 363 which communicates with fluid passage 362. The face seal 360 prevents fluid from flowing between valve bore 361 and IRV body 351. The IRV ball 358 is biased against ball seat 359 by ball guide 357 placing force against ball 358 as a result of spring 356. The ball guide 357 and ball 358 may be considered one example of a valve stem engaging ball seat 359. Spring 356 is compressed in the valve body central passage by IRV set screw 353 acting on spring ball 355 which in turn, compresses spring 356. A lock screw 354 keeps set screw 353 in its selected position and the IRV cap 352 seals the central passage of valve body 351.

It may be envisioned how the adjustment set screw 353 selects the magnitude of force (pressure) acting on IRV ball 358 before it disengages from ball seat 359 and allows fluid to flow through inlet channel 363. Likewise, it can be seen that once drive fluid pressure has dislodged ball 358 from seat 359, fluid is able to flow into side passage 342. Thus, a fluid path is created between the drive fluid side of the pump and the side passage 342 when the ball 358 is moved from seat 359.

FIG. 16B also illustrates how the indicator assembly 335 is also based upon an assembly bore 339 being formed in the drive fluid body plate 205D. Similar to IRV bore 361, assembly bore 339 communicates with side passage 342 and also the return passage 345 which ultimately communicates with drive fluid reservoir 280 and burp well 295 as suggested in FIG. 16A.

Positioned within assembly bore 339 is the indicator body or housing 336. The indicator housing 336 includes housing central channel 344 ultimately communicating with return passage 345. The housing central channel 344 may also communicate with side passage 342 via an aperture within housing 336 (hidden from view in the Figures). Housing central channel 344 includes at least one necked-down section 346 transitioning from a first channel 344A diameter to a second, smaller channel 344B diameter.

An indicator spool 337 is positioned within indicator housing 336. Indicator spool 337 is retained in housing 336 by indicator cap 338 which includes a central aperture allowing a front neck section 347 of indicator spool 337 to extend through cap 338. The embodiment of indicator spool 337 seen in FIG. 16B further includes a first or main diameter portion 348A of indicator spool 337, a second smaller diameter portion 348B, and a still smaller third diameter portion 348C. A piston surface 341 is formed where the spool transitions from first diameter 348A to the smaller second diameter portion 348B (also sometimes referred to as a first transition point on the spool). Indicator spool 337 further includes a second transition point 343 where the spool transitions from the second diameter portion 348B to the third smaller diameter portion 348C.

In operation, indicator neck 347 on spool 337 will typically be in the inward or non-indicating position (not shown in the Figures), i.e., indicator neck does not extend beyond cap 338 and the second diameter portion 348B is positioned within the smaller housing central channel section 344B. It will be understood that the diameter of spool portion 348B is closely matched with channel section 344B, but still able to freely slide in channel section 344B. Thus, channel section 344B is effectively blocked to fluid flow by spool portion 348B. If the drive fluid pressure rises to a magnitude greater than the closing force exerted on IVR ball 358, the ball will disengage ball seat 359 and the drive fluid will enter channel 363 and flow into side passage 342 (or transfer pressure to fluid already in side passage 342). Fluid pressure is then transferred to housing central channel section 344A where it will act on piston surface 341, creating a force tending to move indicator neck 347 out of the aperture in cap 338 to the indicating position (sometimes referred to as the “alert status”). The spool seal 340 will provide some frictional resistance to the movement of indicator spool 337 and will tend to maintain indicator neck 347 in its indicator position even after pressure is reduced on piston surface 341. As indicator spool 337 moves forward, spool section 348B moves out of channel section 344B, and channel section 344B becomes more open because it is now engaged by the small diameter spool section 348C. The pressurized drive fluid now passes through the space between channel section 344B and spool section 348C and into reservoir return passage 345. Once the pressure acting on piston surface 341 has been relieved, indicator neck 347 may be pushed back flush with cap 338 by overcoming the frictional resistance of spool seal 340 (sometimes referred to as the “normal status”). In one example, this force will be at least a few ounces, but typically less than several lbs, e.g., 6 ounces to 1 lbs.

Although the indicator has been described in terms of a mechanical spool which is visually detected, the indicator could be any conventional or future developed indication technique. Likewise, although the indicator has been described in the illustrated embodiment as a separate device, it may be incorporated into the IRV itself in other embodiments in order to reduce costs or for other reasons.

FIG. 17 schematically illustrates an alternative method of securing a diaphragm assembly 250 between the body plates 205A and 205D. It will be understood that body plates 205A and 205D are “schematically” represented in the sense that they are merely shown as blocks with pumped fluid passage 256A and drive fluid passage 256B communicating through the respective blocks. Naturally, the details of constructing the pump head (e.g., such as seen in FIG. 12) would be incorporated into a pump using the concept described in reference to FIG. 17.

The body plates 205A and 205D in FIG. 17 each include the channel 259 formed along their outer radius. Positioned within each channel 259 is beveled compression ring 260. Compression ring 260 is beveled in the sense that it has a frusto-conical shape which gives it a spring characteristic much like a “Belleville” washer (also known as a coned-disc spring or conical spring washer). The side of compression ring 260 facing the diaphragm assembly 250 includes a series of concentric ridges or teeth 261. It may be envisioned how the clamping together of body plates 205A and 205D places a compressive force on compression ring 260. As compression ring 260 is compressed, it flattens and the teeth 261 exert an outward, circumferentially uniform, radial force on diaphragm assembly 250. This outward radial force place a circumferentially uniform tension on diaphragm assembly 250. In the embodiment of FIG. 17, the seal groove 262 is formed behind compression ring 260 and the 0-rings 263 form a seal between the rear surface of compression ring 260 and the body plates. Likewise, the teeth 261 act to form a seal between compression ring 260 and diaphragm assembly 250.

FIG. 18A illustrates a schematic representation of an alternate method of securing a diaphragm assembly between body plates 205A and 205D. In this embodiment, the channels 275 formed in the body plates have inclined walls or surfaces 276 sloping away from diaphragm assembly 250. Positioned within channels 275 are a plurality of wedge members 270, which include an inclined surface 271 complementing the inclined walls 276 of channels 275. In the FIG. 18A embodiment, the front (i.e., facing diaphragm assembly 250) surface 272 of wedge members 270 are substantially flat or vertical. As suggested in the planar view of FIG. 18B, a plurality of wedge members 270 will be positioned around the circumference of the body plates forming a broken ring assembly. In the illustrated embodiment, a biasing member 277 is positioned around the wedge members 270 and will urge the wedge members inwardly to maintain their relative positions. In one example, the biasing member is a conventional o-ring or other band of elastomeric material. Also seen in FIG. 18A are sealing o-ring 263 positioned on body plates 205A and 205D radially inward of wedge members 270.

In operation, it can be envisioned how compressing the body plates together will urge wedge members 270 radially outward as a result of the inclined surfaces of wedge members 270 and channels 275 acting against one another. At the same time, the vertical surfaces 272 of wedge members 270 are being urged against diaphragm assembly 250. This combination of forces will generate a radially outward tension on diaphragm assembly 250. Likewise, the O-rings 263 are pressed against diaphragm assembly 250 to form a fluid tight-seal. Those skilled in the art will recognize that the FIG. 18 embodiment creates an adequate metal-to-metal gripping surface (i.e., metal wedge member to metal diaphragm member) along the outer edge of the diaphragm assembly without attempting to create a metal-to-metal seal (e.g., in the manner that the teeth 261 on compression ring 260 create a seal against the diaphragm assembly). Thus, in the FIG. 18 embodiment, the clamping force may be greatly reduced, since it is only necessary to maintain the position of the diaphragm assembly, not create a metal-to-metal seal.

FIG. 19 illustrates a schematic diagram of a sensor monitoring circuit utilized in one embodiment of the invention. FIG. 19 suggests a diaphragm pump head 201 having a series sensors 220 to 222. The sensors communicate with a controller 223, which in turn operates an alarm 224 and a shut-off switch 226. In this embodiment, sensor 220 is positioned to detect an overpressure in the drive fluid, sensor 221 is position to detect leaks in the diaphragm assembly, and sensor 222 is positioned to detect a low fluid level in the drive fluid reservoir. As one example, sensor 220 could be a pressure transducer position along air bleed line 326 (see FIG. 12), sensor 221 could be a pressure transducer positioned along the fluid path of pressure gauge 265 monitoring the diaphragm leak detection circuit, while sensor 222 could be a level sensor, e.g., an optical level sensor, positioned within fluid reservoir 280 (see FIG. 12).

Each sensor will be connected to the controller 223. The controller may be programed to activate alarm 224 when the sensors detect predefined conditions (a “trigger event”). The alarm 224 may provide different alert signals based upon which sensor controller 223 indicates has detected a trigger event. Likewise, certain predefined conditions detected by the sensors may cause controller 223 to activate shut-off switch 226. As one nonlimiting example, shut-off switch 226 could interrupt power to the electrical driver operating the plunger if a sensor detected a low fluid level in the reservoir. 

1-7. (canceled)
 8. A diaphragm pump comprising: a. a pump head including a diaphragm assembly; b. a drive fluid reservoir communicating with the pump head; c. a plunger extending thought the fluid reservoir and directing drive fluid against the diaphragm assembly; and d. a bushing between the diaphragm assembly and the fluid reservoir, the bushing including a main plunger passage into which the plunger travels; e. wherein (i) a surface of the bushing engaged by the plunger, and (ii) a portion of the plunger engaging the surface, both comprise a ceramic.
 9. The diaphragm pump of claim 1, wherein the main plunger passage having a tolerance of less than 0.5/1000 of an inch, diametrically, with respect to the plunger.
 10. A diaphragm pump comprising: a. a pump head including at least one body plate with a pumped fluid face and at least one body plate with a drive fluid face; b. a diaphragm assembly positioned between the pumped fluid face and the drive fluid face; c. wherein the pumped fluid face has positive profile biasing the diaphragm assembly in a direction toward the drive fluid face.
 11. The diaphragm pump of claim 10, wherein the positive profile is positioned on an outer radial half of the pumped fluid face.
 12. The diaphragm pump of claim 10, wherein the positive profile is positioned on an outer radial quarter of the pumped fluid face.
 13. The diaphragm pump of claim 10, the diaphragm assembly includes at least two metal diaphragms.
 14. The diaphragm pump of claim 10, wherein the diaphragm assembly comprises a third, leak detection diaphragm.
 15. The diaphragm pump of claim 10, wherein an outer radial portion of the pumped fluid face includes a convex shape and an inner radial portion of the pumped fluid face has a concave shape.
 16. A diaphragm pump comprising: a. a pump head including a pumped fluid side and a drive fluid side separated by a diaphragm assembly; b. a burp valve assembly hydraulically communicating with the drive fluid side of the diaphragm assembly and comprising; i) a valve housing having an upper and lower valve seat; ii) a valve ball positioned to move between sealing engagement with the upper and lower valve seat; and iii) a valve poppet positioned at least partially in the valve housing and moveable to engage the valve ball and displace the valve ball from engagement with the upper seat.
 17. The diaphragm pump of claim 16, wherein the valve housing is at least partially covered by a drive fluid.
 18. The diaphragm pump of claim 16, wherein the valve poppet is biased out of engagement with the valve ball.
 19. The diaphragm pump of claim 16, wherein in a fluid path is formed through the lower valve seat to an exterior of the valve housing.
 20. The diaphragm pump of claim 16, wherein the distance between the upper and lower valve seats is less than twice the diameter of the valve ball.
 21. The diaphragm pump of claim 16, wherein the burp valve assembly is positioned in a burp well and the burp well is in fluid communication with a drive fluid reservoir of the diaphragm pump.
 22. The diaphragm pump of claim 16, wherein a passage from a drive fluid side of the pump head communicates with the lower valve seat.
 23. A diaphragm pump comprising: a. a pump head including a pumped fluid side and a drive fluid side; b. an internal relief valve hydraulically communicating with the drive fluid side of the pump head and comprising: i) a valve bore formed in the pump head and communicating with the drive fluid side of the pump head; ii) a valve housing with a valve seat inserted with the valve bore with the valve seat communicating with the drive fluid side of the pump head; iii) a valve stem biased against the valve seat in order to bias the internal relief valve in a closed position; and iv) a side passage communicating with the valve bore and forming a fluid path to the drive fluid side of the pump head when the valve stem is pushed out of engagement with the valve seat; c. an indicator assembly comprising: i) an indicator bore formed in the pump head; ii) a passage establishing a fluid path between the indicator bore and the side passage in the valve bore; iii) an indicator responsive to pressurized fluid entering the indicator bore from the side passage in the valve bore.
 24. The diaphragm pump of claim 23, wherein the indicator includes spool sliding within the indicator bore in response pressurized fluid entering the indicator bore.
 25. The diaphragm pump of claim 24, wherein the spool include a larger diameter portion and a smaller diameter portion with a piston surface formed at a transition from the smaller to larger diameter portion.
 26. The diaphragm pump of claim 25, wherein an indicator housing is positioned within the indicator bore and the spool Is positioned within the indicator housing. 27-46. (canceled)
 47. The diaphragm pump of claim 10, wherein the center of the diaphragm assembly is closer to the drive fluid face than the pumped fluid face when the diaphragm assembly is in a resting position. 